This invention relates to a process for alkylating an alkylatable isoparaffinic hydrocarbon with olefinic hydrocarbons. In another aspect, this invention relates to a process and apparatus for the alkylation of isoparaffins with two or more different olefins with a liquid acid alkylation catalyst. In yet another aspect, this invention further relates to a cyclic process for the alkylation of an isoparaffin with different olefins at different temperatures at different periods of time in the same reactor. In yet another aspect, this invention relates to the alkylation of an isoparaffin with a first olefinic reactant, continuously separating the resultant alkylation effluent into a first liquid hydrocarbon phase and a liquid acid phase, and continuously recycling the acid phase to the alkylation reactor, and, during the second period of time, recycling said first liquid hydrocarbon phase to be reacted with a second olefinic reactant. In still another aspect, this invention relates to a cyclic alkylation reaction wherein an isoparaffin is utilized cyclically with two different olefinic reactants in the same reactor at two different periods of time, and the acid catalyst is continuously separated during both periods of time, and being either heated or cooled to the optimum temperature required for each separate alkylation. In yet another aspect, this invention relates to an apparatus for the alkylation of an isoparaffin comprising only one alkylation reactor, three surge zones, and a fractionator for separating the various components of the alkylate stream.
Alkylation of isoparaffinic hydrocarbons, such as isobutane, isopentane, and the like, with olefinic hydrocarbons, such as propylene, butylene, amylenes, and the like, is well known as a commercially important method for producing gasoline boiling range hydrocarbons. Generally, the alkylation of isoparaffins with olefins is accomplished by contacting the reactants with an acid-acting catalyst, such as liquid hydrofluoric acid, settling the mixture to separate the liquid catalyst from the liquid hydrocarbons, and further separating the hydrocarbons, e.g., by fractionation, to recover alkylate product, and to recover unreacted isoparaffin for recycle to alkylation. The alkylate is typically a mixture of isomers of heptane, octane, etc., with the exact composition depending upon the isoparaffin and olefin reactants used. Various types of catalysts have been utilized in this reaction, including sulfuric acid, hydrofluoric acid, phosphoric acid, certain halosulfonic acids, and aluminum chloride. The preferred catalyst is hydrofluoric acid because of the relative ease with which it can be used and reused and because of the superior quality of the alkylate that is produced.
It is the usual practice to alkylate an isoparaffin with two different olefins in the same reactor at the same time, or in separate reactors, as it is known that separate alkylations of, for example, butylenes and propylene, produce higher octane total alkylate than the alkylate made by charging butylenes and propylene as combined olefins to the alkylation reactor. The processes disclosed in U.S. Pat. Nos. 3,158,661 and 3,787,518 exemplify an alkylation reaction wherein butylene olefin reactants and propylene olefin reactants are reacted in separate HF alkylation reactors. Due to the expense of providing separate reactors and settlers for the two different olefins, however, the economics of this type of process are not as favorable as a process in which only one alkylation reactor is necessary in order to obtain a high octane alkylate product. The advantage of the two-reactor alkylation system, however, is that one can control the individual reaction temperature as desired to allow each alkylation to run at the optimum temperature and thereby produce an optimum product.
U.S. Pat. No. 3,998,893 discloses a one-reactor system for the alkylation of olefins. The process involved, however, does not separate out the hydrofluoric acid catalyst from the hydrocarbon between olefin injections, and, therefore, must take the temperature from the first alkylation as a temperature to start the second alkylation. The process can only be used as effectively as a two-reactor system, therefore, if the optimum temperature for the first olefin to be alkylated is lower than that of the second olefin, otherwise, the process can have a detrimental effect on the quality of the alkylate product.
Accordingly, it is an object of the invention to provide an improved process and apparatus for alkylating one or more isoparaffins with at least two different olefins.
Another object of the present invention, is to provide an economical process in conjunction with a simplified apparatus for the alkylation of an isoparaffin with at least two different olefins.
Yet another object of the present invention is to provide an improved process for the alkylation of an isoparaffin with at least two different olefins wherein each olefin is reacted at the optimum temperature.
Another object of the present invention is to provide an economical process and simplified apparatus for the alkylation of an isoparaffin with at least two different olefins wherein the olefins can be reacted separately and at their optimum temperature in the same reactor.
Other objects, aspects, and the several advantages of this invention will be apparent to those skilled in the art upon a study of this disclosure, the appended claims, and the drawing.